1. Field of the Invention
An inductively coupled lock with a key providing a binary signal to the lock which responds only to a specific signal in opening the lock.
2. Description of the Prior Art
Electronic lock systems are well known in the prior art. These take various forms. Generally, the key or a coded device is placed within an aperture in the lock portion of the system. The lock is designed to then discriminate against all but a predetermined code. In the specific case of electronic locks, the key is encoded in any number of ways. Some prior art encoding techniques include the provision of punched holes which correspond to electrical probes within the lock. Conductive strips are also utilized, which complete the electrical circuit with the lock. Other methods include an electromagnetic code on the key which is discerned by cooperating circuitry within the lock.
One type of electronic lock system known in the prior art has a key comprising a coil. When the key is placed in close proximity to the lock, a resident circuit within the lock itself is completed causing the lock to open.
These systems are complex and can be costly to construct and maintain. The advantages of electronic locks are many and well known. However, there are certain disadvantages in the presently known electronic lock systems.
First, the electronic lock requires a source of electricity. A number of present art locks have the power source within the lock portion of the system. This is frequently inconvenient and impractical for certain applications where the lock itself is inaccessable to a power source.
Many presently known electronic lock systems are generally designed to have a large number of replaceable or recodeable keys capable of fitting a relatively small number of locks. These locks have the sophisticated mechanisms contained within them along with a power source. This is inconvenient and impractical in cases where one key can fit many locks and the locks themselves are subject to severe abuse and located in places inaccessable to a power supply.
Another problem commonly associated with electronic systems is that the receiving aperture in the lock for the key is subject to tampering. The insertion of foreign material into the receiving aperture of a sophisticated electronic lock could severely damage or destroy many conventional electronic locks by fouling contacts or destroying electromagnetic sensors. Any lock used in a public place is subject to such destructive tampering.
Another problem encountered with transmitting an electrical signal from the key to the lock is that in using a unique waveform, the number of different types of waveforms which can be used are greatly limited. Furthermore, where part of the electronics are analog, such as the shape and magnitude of the waveform, the long term stability of the circuitry may require periodic adjustment.
Therefore, in view of the many problems existing in the lock industry, it can be seen that there is a need for an electronic lock system wherein the lock part is simple to construct, requires no built in power source, is relatively tamperproof, has a very large number of combinations of predetermined signals that can be used to activate the lock and contains no circuitry with long term stability problems. The key part of such a desirable system could contain the power source for lock operation and be capable of opening the lock without being inserted in an aperture of the lock.